The rolling of long metal products provides the progressive reduction of the thickness of the metal products by means of cylinders, rolls, or rotating rings of rolling apparatuses or stands along which the metal product is fed and rolled.
It is known to use, for example in the final steps of the rolling process, one or more guide apparatuses, also called roller guides, each configured to guide and support the metal products entering or leaving the rolling apparatus, for example a finishing stand.
Known guide apparatuses each comprise at least one pair of guide rolls mounted idle on a support body and having axes of rotation orthogonal to a rolling axis.
Examples of guide apparatuses provided with two guide rolls are described in documents U.S. Pat. No. 4,790,164, WO-A-00/66288 and JP-A-2015/231636.
In particular, U.S. Pat. No. 4,790,164 describes a guide apparatus provided with a sensor for each guide roll. In U.S. Pat. No. 4,790,164 it is claimed that only one sensor could be sufficient, given that the two guide rolls are disposed so that the pressure loads are equal to each other. The output pressure signal, or each output pressure signal, detected by the sensor can be fed to an indication or recording mean, to adjust the guide rolls by adjustment screws.
U.S. Pat. No. 4,790,164 also describes that it is also possible to provide the output signal of the sensor or sensors, to a drive for the adjustment of the guide rolls or their support arms, in order to maintain the original pressure of the guide rolls constant on the material passing through them. The presence of a single drive for both adjustment screws allows a substantially symmetrical adjustment of the loads acting on the guide rolls, precisely because of their disposition as described above.
Moreover, U.S. Pat. No. 4,790,164 provides, in another embodiment thereof, that the support arms are each provided with a horizontal adjustment screw and a clamping screw to clamp the adjustment screw. The presence of a clamping screw, however, does not allow to associate with the adjustment screws a drive to remotely automate the adjustment of the roller guide gap of the metal product, since the rotation of the adjustment screw is prevented by the clamping screw.
The guide apparatus described in WO-A-00/66288 comprises a support structure, a pair of support arms with an oblong development pivoted in their centerline and to the support structure, and guide rolls installed at one end of the support arms. The support arms comprise, at the opposite end with respect to that where the guide rolls are installed, adjustment screws to adjust the passage gap between the two guide rolls.
A force detector is also associated with each support atm, provided to detect the forces acting on each guide roll.
The guide apparatus described in WO-A-00/66288 also comprises a single adjustment device, which can also be motorized, to adjust the size of the passage gap between the guide rolls.
The single adjustment device allows to adjust the position of both support arms of the guide rolls in a synchronized and conjoint manner.
JP-A-2015/231636 describes another guide apparatus which comprises a pair of guide rolls each of which is installed on a respective rotation pin attached to a support structure of the guide apparatus.
On each rotation pin, a respective toothed wheel is installed, integrally and eccentrically.
The toothed wheels both engage on a single toothed rack which is moved linearly, determining a consequent rotation of the toothed wheels. The rotation of the toothed wheels determines a consequent eccentric rotation of the rotation pins, obtaining an adjustment of the passage gap of the metal product. The linear movement of the rack is determined by a hydraulic piston. This adjustment mode, however, is not precise and adjusts the position of both support arms.
In the rolling of metal products, for example with a diameter comprised between 4 and 170 mm or more, and where rather narrow dimensional tolerances are required, the use of guide apparatuses is also known, associated with the rolling apparatuses and having three, four or more guide rolls installed on support arms, in turn associated with a support body.
It is also known that rolling apparatuses are also configured to exert quite high compression actions on the metal product, for example by means of three, four or more rolling rolls, and that the section of the metal product exiting from a rolling stand can also have a non-regular shape and size, for example ovalized, diamond-shaped, and therefore not round. For this purpose the guide rolls of the guide apparatus are also disposed so as to define between them a roller guide gap of a shape and size suitable for those of the metal product that is to be guided.
It is also known that the guide apparatus must be installed in such a way that the roller guide gap between the guide rolls is aligned with the axis, that is, with the rolling channel of the rolling apparatus. This allows to feed and guide the metal product correctly toward the rolling apparatus.
An unaligned feed of the metal products with respect to the rolling apparatus determines an incorrect rolling of the metal product and therefore does not respect the dimensional and/or geometric tolerances of the product; it also determines a production of non-linear rolled products which, due to their distortion, must be discarded.
The misalignment of the guide apparatus with respect to the rolling apparatus, moreover, causes the onset of different stresses on the guide rolls, with consequent non-uniform wear of one guide roll with respect to the other.
Moreover, the different stresses between the two guide rolls are also transferred to the components connected to them, for example to the support bearings of the guide rolls, with a consequent reduction in their working life.
It is known that, at present, the alignment between the roller guide gap of the guide rolls and the rolling axis of the rolling apparatus is carried out on the bench, that is, with the guide apparatus not installed on the rolling machine.
Alignment is carried out using a calibration apparatus that simulates the passage of a product to be rolled and the position of the guide rolls is adjusted as a function of this.
However, even if the calibration can be carried out with care and the elements that attach the guide apparatus to the rolling machine comply with very strict tolerances, the alignment of the guide apparatus, once installed in the rolling machine, will always deviate from the alignment defined in the calibration step. This also in relation to deformations and/or settling to which the different components of the guide apparatus are subject.
Guide apparatuses are also known, provided with detection devices, for example load cells, strain gauges, or other detection devices, for example based on the Wheatstone bridge principle, which are associated with support arms of the guide rolls and configured to detect the stresses to which the latter are subjected during use. Depending on the data detected by the detection devices, the amplitude of the roller guide gap and/or the position of the entire guide apparatus with respect to the rolling machine is adjusted.
This manufacturing solution, however, does not allow to obtain a correct calibration, and leads to the generation of metal products that do not meet the quality requirements.
Furthermore, this type of guide apparatus cannot be adopted for large-sized metal products.
For large-sized metal products, where very strict tolerances are normally required, it is in fact required that the guide rolls exert an action to contain the metal product and, therefore, the use of guide apparatuses with three, normally four guide rolls is often required, which are installed on a common support body and located on the periphery of the metal product to exert a correct guide action.
In this case, a movement of the entire support body cannot solve the problems of alignment of the roller guide gap with the rolling gap, for example due to the fact that one or more of the guide rolls are not positioned correctly and therefore, they interfere with the movement of the metal product, or do not exert a guide and holding action.
Moreover, during the work cycles, the support bodies are subject to mechanical and/or thermal expansion, also variable depending on the material of which they are made, which determine further interference in the guide action.
In these solutions, therefore, the guide apparatus must be removed from the rolling machine to perform an additional calibration.
To this must also be added the fact that the manual adjustment members of the guide rolls cannot be accessed by the operators when they are installed on board the rolling machine.
Moreover, during the rolling process, the rolling rolls are subject to rather considerable processes of wear which lead to the production of increasingly large products.
The increase in size of the metal product also induces further stresses on the guide rolls, with consequent wear.
One purpose of the present invention is to provide a guide apparatus which allows to feed, in a precise, controlled and aligned manner the metal products in a rolling apparatus.
Another purpose of the present invention is to provide a guide apparatus for metal products which allows to adjust the shape and size of the roller guide gap defined between the guide rolls.
Another purpose of the present invention is to provide a guide apparatus which allows to adjust the position of the guide rolls at any time, even with the guide apparatus installed in the rolling machine, or during rolling.
Another purpose of the present invention is to provide a guide apparatus which allows to obtain high quality metal products, that is, which satisfy the desired requirements of dimensional and/or geometrical tolerance.
Another purpose of the present invention is to provide a guide apparatus which allows to increase the working life of the components, or parts of them, by reducing maintenance operations.
Another purpose of the present invention is to perfect a method to guide metal products which allows to adjust the shape and size of the roller guide gap defined between the guide rolls, at any time, even with the guide apparatus installed on a rolling machine and/or during use.
Another purpose of the present invention is to perfect a method to guide metal products which allows to obtain high-quality metal products, and which allows to increase the working life of the components of the guide apparatus.
The Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages.